The San Gabriel Valley is one of the principal valleys of Southern California, lying generally to the east of the city of Los Angeles. Surrounding features include:  San Gabriel Mountains on the north, San Rafael Hills to the west, with Los Angeles Basin beyond; San Fernando Valley and Crescenta Valley farther to the northwest, Puente Hills to the south, with the coastal plain of Orange County beyond, Chino Hills and San Jose Hills to the east, with the Pomona Valley and Inland Empire beyond. The valley derives its name from the San Gabriel River that flows southward through the center of the valley, which itself was named for the Spanish Mission San Gabriel Arcángel originally built in the Whittier Narrows in 1771.At one time predominantly agricultural, the San Gabriel Valley is today almost entirely urbanized and is an integral part of the Greater Los Angeles metropolitan area. It is one of the most ethnically diverse regions in the country. About 200sqmi in size, the valley includes thirty-one cities and five unincorporated communities.